chapter 42: Neural Regulation and Drug Effects on the Nervous System

Nervous system

receive information: environmental stimuli (internal/external)

translate information: evaluate stimuli

send response: initiate and send to effector, coordinate rapid, immediate responses

Nerve nets

interconnected neurons, no central control point

movement and response to stimuli

response from multiple directions, bidirectional

animals with nerve nets

clade radiata, phylum cnidaria (jellyfish)

-slow net: coordinates tentacles; fast net: coordinates swimming

clade bilateria, phylum echinodermata (starfish)

-radial nervous system: coordinates tube feet and arm movement

Bilateral nervous systems

structure: control point (ganglia/brain), interconnected neurons

function: integration (stimulus, intensity, direction), coordination of movement and response

response: localization of stimulus, unidirectional neurons (absolute refractory period), separation of function

animals with bilateral nervous system

platyhelminthes, annelida, arthropoda, cephalopoda

platyhelminthes nervous system

cerebral ganglia, primitive brain

nerve cords: two solid, ventral, longitudinal

neuron types: all 3 types

behavior: many senses, learning, directed movement (taxis)

annelida nervous system

brain(coordinated, adaptive response), ganglion (segmented control)

nerve cord: solid, ventral

behavior: forward movement with segments, elongating and shortening at times

arthropoda nervous system

insects have the largest brain in phylum

have more neurons for learning, memory olfactory processing (foraging ants)

cephalopods nervous system

brain has lobes and intricate folds, regions well developed for specific functions

senses well developed

octopus

phylum cephalopoda

greatest brain size

significant ability to learn, perform difficult tasks

color, skin, shape changes

afferent nervous system

sensory

efferent nervous system

motor

CNS

integrates information and sends responses

brain (cranium) and spinal cord

12 pairs of cranial nerves and 32 pairs of spinal nerves

nerves function to connect to periphery

PNS

connects to but lies outside of brain and spinal cord

carry information to and from body parts and regions

divisions: somatic and autonomic (parasympathetic and sympathetic)

somatic nervous system

part of PNS

skeletal muscle and skin

voluntary muscle movement - conscious activities

autonomic nervous system

part of PNS

involuntary response

controls internal organs

divides into parasympathetic and sympathetic

parasympathetic nervous system

relaxing system

maintain minimal energy levels

resting and digesting

sympathetic nervous system

alert system

mobilize energy, decrease non vital functions

stimulate adrenal gland to release epinephrine

fight or flight

Vertebrate nervous system

Includes the CNS and PNS

Reflexes

protective function

innate behavior

PNS connects to CNS

involve cranial or spinal pathways

Muscle spindle reflex (glogi tendon stretch reflex)

spinal reflex

monosynaptic, unisegmental, ipsilateral (all on one side), reciprocal innervation (opposing muscle groups)

contraction opposite to the stretch initiator

Withdrawal reflex

spinal reflex

excitatory and inhibitory interneuron

withdraw on stimulated side of body (ipsilateral), extension on opposite side of body (contralateral)

intersegmental response (both sides of cord)

same input- both side effected

Cross extensor reflex

When one limb is withdrawn, the opposing limb extends to support the body

Cerebrum

most superior part and largest brain mass

second largest surface area

cortex: grey matter, cell bodies and dendrites, information processing

inner portion: mostly white matter, axons that connect various parts of brain

CNS protective barriers

The protective barriers of the central nervous system.

Receptor site

The location where drugs exert their effects.

Receptor affinity

The strength of the binding between a drug and its receptor.

Intracellular drug

A drug that works within cells.

Extracellular drug

A drug that works outside of cells.

Resistance

The reduction in effectiveness of a drug in curing a disease or condition.

Brain

a centralized control/integration point of the nervous system

Contralateral

when sensory and motor neurons enter and exit on opposite sides of the spinal cord, integration happens in the cord during the crossover to the other side

Decussation

crossing over of spinal nerve tracts that occurs in the medulla

Ganglion

a group of nerve cell bodies, in the vertebrate CNS they are located peripherally

Gray matter

nervous tissue that contains only unmyelinated axons, cell bodies, and support cells

Gyrus

the convoluted brain tissue of the cerebrum

Hemisphere

one half (left or right) of the cerebrum

Ipsilateral

when sensory, integration and motor neurons connect on one side of the spinal cord

Sulcus

furrows (dips between the gyri) that run throughout the cerebrum

Cerebral ganglia

concentration of nerve cell bodies; primitive brain - control system

Cerebellum

located dorsal to pons and medulla; second largest mass of the brain, involved in hand-eye coordination, balance, and posture

Medulla

part of both hindbrain and brain stem; regulates life-sustaining functions such as heart rate and respiration

Pons

lies superior to medulla and anterior to cerebellum; connects higher brain centers with the cord

helps regulate respiration

Midbrain

lies superior to pons; involved in motor movement of eyes and auditory processing

forebrain

at top of brain stem and includes thalamic structures: cerebral hemispheres and limbic system

Thalamus

has motor and sensory connections with the cerebral cortex; filters and sorts stimuli

crude sense of stimuli

Hypothalamus

regulates autonomic and somatic responses; controls emotions and produces hormones; regulation of endocrine functions; regulation of body temps; hunger and thirst center

epithalamus

regulates sleep-wake cycle and emotions

right hemisphere

emotional processing

visual-spatial tasks - facial recognition

left hemisphere

controls language, decision making, fact recovering

Corpus callosum

large band of white matter forming roof of lateral ventricles; connects the two cerebral hemispheres

Wernicke's area

integrative speech area located in the left temporal lobe; responsible for understanding language

Broca's area

located in the frontal lobe of the dominant hemisphere; involved in the ability to produce clear speech

Frontal lobe

most anterior lobe and the largest; involved in planning and executing movement and complex functions

Parietal lobe

integrates sensory input; identifies objects and spatial relationships

Temporal lobe

functions include short term memory, speech, and musical rhythm

Occipital lobe

houses the primary visual center; processes and integrates visual signals

Cerebral cortex

functionally divided into sensory areas, motor areas, and association areas

Central sulcus

lies between frontal and parietal lobes; boundary of somatosensory and somatomotor cortex

Primary motor cortex

runs anterior to precentral gyrus; controls voluntary movement

Primary sensory cortex

runs posterior to precentral gyrus; receives information from sensory structures

non-surface lobe

insula lobe

functions: emotions, visceral response

limbic system

ring of forebrain structures surrounding the brain stem

behavioral and emotional response, motivation (dopamine stimulates motivation)

Spinal cord

Location: inside vertebrae - from base of brain, foramen magnum to second lumbar vertebrae

Spinal cord function

Connect periphery and brain (afferent and efferent)

Structure of spinal cord

Central canal surrounded by H shaped gray matter - reaches dorsal surface

White matter

Surrounds gray matter and conducts impulses to and from brain

myelinated

Tract

Collection of axons with a common origin and destination

Ascending tracts

Tracts that carry impulses up to the brain

Descending tracts

Tracts that carry impulses down from the brain

CNS protection

Bone and three connective tissue layers (Meninges): Dura mater, Arachnoid mater, Pia mater

Cerebral-spinal fluid

Produced by choroid plexus and circulates in subarachnoid space, central canal of cord, and ventricles in brain

Blood-brain barrier

Tight junctions between capillaries regulate exchange between blood and CNS

Drug defined

Substance that has a physiological or psychological effect when ingested

Prescribed drugs

~25% of prescribed drugs alter psychological conditions

Drug actions

Receptor site: drugs act at specific locations

Agonist

Binding causes effect in target similar to the normal activating molecule

Antagonist

Binding blocks binding of normal effector molecule

Length of effect

Depends on reception affinity and circulation concentration of drug

Physical dependence

Drugs cause physiological changes that result in withdrawal symptoms when drug use is discontinued

Drug addiction

Compulsive use of a drug despite negative effects

Tolerance

Occurs when body's response decreases and greater amounts may be needed to obtain the same effect

Atropine

Cold medications - reduces secretions, dilates pupils, low dose slows heartbeat, high dose treats slow heartbeat (brachycardia)

Digitalis

Stimulates heart contractions and cardiac output - used for congestive heart failure

Paregoric

From podium poppy, used to treat diarrhea

Cocaine's action

Stimulates reward pathway but can also cause physical effects such as fast heart rate and sweating

Myasthenia gravis

Autoimmune disease causing muscle weakness due to antibodies attacking acetylcholine receptors

strychnine

binds post synaptic receptor

pest poisons

blocks normal IPSP transmutation

muscle spasm, convulsions death

tetanus

prevents presynaptic relase of inhibitory neurotransmitters

Continued stimulation

Effects like strychnine but different cause

lead

binds volage -gated Ca channels

Affects neurotransmitter release

venom

causes massive release of acetylcholine

Increases Ca increases release of neurotransmitter

Agonist for prolonged depolarization

Muscle paralysis - rigid paralysis

curare

binds postsynaptic receptors and blocks acetylcholine binding

Antagonist to neurotransmitter release

Muscle paralysis - depolarization blocked (flaccid paralysis)